You'll be glad to know that this happened on my 740i too. After a certain mileage, the M62 kills the alternator and does that. I think its b/c it runs so fricking hot! I had the same issue.

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2004 X5 4.8is - X-pipe! V1 hardwired, Invision DVD headrests, N62 Intermediate Levers Fixed! FOR SALE!!! Contact me if interested!

1999 LSB M Coupe - Heavily modified
2008 M5 Sepang/Portland - Bone stock
2010 Mini Cooper S Laurel Sport Edition #1/100
2002 525iTouring - Alpine/Beige